Attention span is a normal function of our brain. Our level of attention of thoughts/objects and/or persons in our environment can be variable from moment to moment, minute to minute, hour to hour, and day to day.
There is a normal waxing and waning of our level of sustained attention span when we are reading, watching, listening, and even talking. On one extreme we can raise our attention level to sustain a maximum visual attention response (stare) to a threatening bee flying around in a room we are in. Nothing else can distract us for that sustained moment or minute. But we are unlikely to be able to sustain a vigilant stare at that bee for an hour or a day. Our attention span would begin to wax and wane by other distractions, plans, or tasks that would enter our mind. On the other end of the extreme scale we try to maintain our maximum level of sustained auditory attention when we are listening on a telephone to a serious family tragedy that just occurred. If a bee suddenly flies and buzzes around our face and ears our level of sustained vigilant auditory attention would be less than a moment or even a few seconds. It would be unlikely that we could sustain our undivided listening attention under these circumstances for a minute or an hour.
These two extreme scenarios are not common or realistic. A more common example would be to imagine two different persons who try to concentrate on reading a book. One type of person is able to read and understand what he is reading in any type environment, e.g., on a busy city public bus, in a NFL stadium at half-time, or while the family is watching a television program in the same room. The other type of person, however, cannot sustain his level of attention in reading a book and cannot understand what he is reading even if he were sitting in a quiet library or when he is home alone.
The most realistic example, however, of demonstrating the variability of attention span skills among people would be in a "classroom-like" environment in which a group of individuals must attempt to pay attention, listen and process information. They are all trying to look, listen, and think at high intensity level in a closely bunched group of 20 to 25 other people. Some can pay attention at a 100% level for 1 to 60 minutes. Some can pay attention at 90% level for 1 to 20 minutes. Some can pay attention at an 80% level for only 1 to 5 minutes. Some can pay attention at a 50% level for only 1 to 2 minutes. And finally some can pay attention at only a 10% level for less than a minute.
As one can see, some have superior attention span abilities and function and others have very poor attention span abilities and dysfunction.
If this group of 20 to 25 individuals mentioned above could all be "relatively" homogenous to a set of other variables such as: intelligence level (IQ), ability to process and understand material they are looking, listening and thinking about (learning ability), absence of any significant physical impairment (e.g., vision acuity, hearing acuity, acute illness or chronic diseases), and absence of any acute/chronic emotional stress in their lives or of a reactive situational behavioral problem, they could then all be measured and compared by their ability to sustain attention.
This would be a measurable function of their brain's attention span. There should be a variable level of individual performance when attempting to perform this task.
This measure can be observed by behavioral characteristics in the "classroom" (a behavioral checklist of how well they look and act like they're paying attention). It can also be measured by their performance level of achievement in the material they are paying attention to (testing the ability to retain facts, directions, assignments).
Decades ago the glucose tolerance test (GTT) had to be standardized and tested among many age groups and with many variable normal and abnormal patients and conditions. Today there is a spectrum and a range of expectation on how one's pancreas will react to a "standard" stimulus over a set time. There are super-normal responses, average normal responses, borderline responses, and mild-severely abnormal responses that can be seen and recorded in a random population. There can even be external and environmental factors which may influence the results of the GTT test on a particular day. The clinician, however, must still be trained and become skilled in interpreting the results as correlated with his observed information of the patient to draw his own impressions and conclusions.
Attention Deficit Disorder is a term which defines a spectrum of conditions that may be the result of 1) a transient situational problem, 2) an external environmental factor, 3) another associated primary brain disorder, or 4) truly be the result of an isolated primary defect in the brain (Primary Attention Deficit Disorder).
At the present time the only means of identifying, measuring and diagnosing a Primary Attention Deficit Disorder is by an extensive history (medical, neurological, psychological, social, familial, educational), observation by others (parents, teachers, relatives, peers, friends, employers), behavioral rating scales, and elimination of other contributing or simulating conditions. There is no current "standard" of physiological measurement to assess the brain's ability to sustain attention span.
If a child had a major "epileptic-looking" event in school the physician would try to obtain as much history and first-hand observation report from the teacher regarding this event. Let's say the teacher completes a "Convulsion Teacher Rating Scale" (CTRS) form and graded her observations on a scale of 0-3. She then asks the parent to take this CTRS form to her physician so that he/she could evaluate the event. Would the physician stop at this point and make his decision, impressions and judgments on this information alone? Would he not consider performing a physiological test such as an EEG to assess whether there was an abnormal electrical dysfunction of the brain that correlated with the subjective observations? What if the history and teacher observations reviewed by the physician sounded like a syncopal attack and the EEG was normal? What if the history and teacher observations sounded like a true generalized tonic-clonic seizure but the EEG was normal? What if the history and teacher observations sounded like a syncopal event but the EEG was abnormal for epileptiform activity? All of these three scenarios occur daily in general pediatric practice and the physician must use his training, skills and experience to make a sound, intelligent judgment and decision based on what he/she hears and observes from all available subjective and objective data.
Today physicians only have the history, reported observations of performance, and subjective behavioral rating scales to diagnose Attention Deficit Disorder. The present invention sets an objective physiologic standard of the brain's ability to react to a stress level of multiple attentional tasks measured over a sustained time. The invention enables the establishment of a normative data pool for a wide spectrum of individuals with many variable factors such as age, grade, gender, associated disorders (including ADD, ADHD, LD, seizures, tic disorders, etc.) and employment.
Testing for Attention Deficits
Over the years tests have been reported to selectively assess the brain's attentional span function. Some of these tests include (Mesulam, M. Principles of Behavioral Neurology, F. A. Davis (1985) pp 76-82.):
1. Continuous Performance Test PA1 2. Digit Span tests PA1 3. Serial Recitation tests PA1 4. Word List Generation Test PA1 5. Trail-Making Test PA1 6. Stroop Test PA1 7. Go-No-Go Paradigm Test
More recently, with the increased interest and research into Alzheimer's Disease (AD), reports have indicated a variety of neuropsychological tests can be useful in diagnosing, tracking progression, and influence of treatments on the clinical course of the disease (Locascio, J. J. et al., Arch-Neurol 52:1087 November 1995).
The Continuous Performance Test was first described by H. Enger Rosvold et al. at Yale University in 1956. (H. Enger Rosvold et al., J. of Consulting Psychology 20:343 (1956)). Rosvold et al. attempted to show that "brain-damaged individuals should show inferior ability" in tasks that require sustained attention when compared to normal individuals. It was their opinion that the paroxysmal bursts of general hypersynchrony brain wave patterns seen in a brain-damaged individual's EEG was a sign of the brain's sudden, brief reduction of attention span. The customary measures of attention span used at that time was the digit span test and digit symbol substitution test taken from the Weschler-Bellevue Intelligence Test. Rosvold et al. theorized that these tests were not prolonged enough to detect attentional deficits in all brain damaged individuals. They, therefore, designed a test which would need "a high level of continuous attention over an appreciable interval of time" and coined the term CPT (Continuous Performance Test). Using a manual revolving drum with 31 letters mounted in two side-by-side columns, the subject looked through a visor and pushed a response key whenever he saw the appropriate target letter appear at 0.92 second intervals. The targets were divided into an "X task" (every time a letter X appeared in the first column of 31 letters rotated at 10 (5 min) or 20 (10 min) revolutions) or an "AX task" (every X following an A letter was the correct response from the second column of 31 letters on the drum). Their results concluded that the brain-damaged group differed from the control groups and that the differences were even more pronounced when the patient performed the more difficult AX task. They suggested that the CPT was reliable and could prove clinically useful in diagnosing "brain damage".
In 1935 John Ridley Stroop attempted to explain the brain's response to associative interference which occurs when a person takes a longer time to name objects aloud than the corresponding words of the objects took to read aloud. It was well known back in the 19th century by psychologists that it took longer to read the color of patches aligned in rows. Stroop discovered a way to analyze this phenomenon by using a compound stimulus of color words which were incongruent to their ink color. In his three experiments he demonstrated that the hardest task was to name the ink colors of incongruent words. He showed that on the average it took a 74% longer time (47 seconds) to name the color of 100 incongruent color words than to name the color of 100 solid squares. This marked interference response has been termed the "Stroop effect."
Since 1935 there has been an overwhelming acceptance of the Stroop Color-Word test as a measure of attention. Many psychologists have concluded that the Stroop test is highly reliable and valid in its interpretive results. (Jensen, A. R., Acta Psychologica 24:398 (65).
Attention Deficit Disorder is usually characterized and defined by three major signs and symptoms: inattention, impulsivity, and hyperactivity. These same symptoms are seen in patients with frontal lobe lesions. Several researchers have attempted to correlate frontal lobe function with several psychometric tests that are more specific to the frontal lobe function (Barkley, R. A., J. of Abnormal Child Psychology 20:163 (1992) and Shue, K. L., Brain and Cognition 20:104 (1992)). Both of the aforementioned reviewers used the Stroop test in their analysis of ADD/ADHD patients.
In 1993 C. J. Bench et al., using PET scanning techniques, measured regional cerebral blood flow in normal subjects while they performed the Stroop Color-Word Test. They found increased activation in the right orbito-frontal area. They concluded that attentional tasks involve the right hemisphere and in particular the medial frontal structures of the brain.
The inventors have developed a modified CPT form of the Stroop test to measure the attentional function of a wide range of population based on the realizations that: 1) the above research shows that attention function most likely predominates in frontal lobe areas, 2) children with ADD/ADHD simulate some of the behavioral features of frontal lobe damaged patients, and 3) the Stroop test shows activation uptake in the frontal lobe during a PET Scan.
Currently there are other CPT tests which are used to assess patients with the ADD/ADHD syndrome. Most attempt to present a single visual stimulus which the patient must concentrate on and react over a prolonged time. There is no current test which attempts to have the patient concentrate and react to a multimodal stimuli.
Teachers and parents universally complain of two specific problems in their ADD/ADHD children: 1) "they never listen to what I say," and 2) "they can never follow more than two tasks I ask the child to do." Parents never say, "my child doesn't look at me." Parents almost always say, "my child can only do one thing at a time." Therefore the present invention attempts to present both a listening target and a visual target delivered randomly over a sustained time duration. A third component of a thinking task is incorporated into the visual target by utilizing the Stroop format effect. Thus the present invention tests a child's ability to sustain his attention to a combined listening, looking and thinking task. This is similar to the attention stress required in the classroom.